The present invention relates to a method and apparatus for encoding asynchronous data signals for data processing and also a method and apparatus for decoding the encoded signals produced by the encoder apparatus.
With the diversification of communications networks in recent years, demand has been on the increase for data processors which are capable of attending to asynchronous data signals having unequal bit rates and phases. In such a processor apparatus, input data signals are processed after they are converted (coded) to code sequences or the like since it is not possible to synchronize each and every input data signal.
The multipoint sampling is a technique for coding data signals in which a plurality of input data signals are sampled with a high-speed common clock and converted to code sequences having an identical speed to be given a desired processing. After processing, the code sequences of the sample data are decoded.
While the multipoint sampling has an advantage that an encoder can be simply constructed with an AND gate which assigns one of the inputs to the data and the other to the sampling clock, it also has the disadvantage of an increase in the sample data involved in the increasing of the sampling frequency, which contributes to the reduction of a phase difference between an original signal and decoded signal. For example, assuming that an input data signal with a bit rate fo is sampled with a sampling clock signal with a frequency of 16 fo, the quantity of data to be processed amounts to 16 times that of the original data. The sample data increase necessarily leads to such problems as an increase in the size of the apparatus for processing the data and a reduction in the processing speed.